Two-Dimensional Hybrid Perovskite-Type Ferroelectric for Highly Polarization-Sensitive Shortwave Photodetection

Two-dimensional (2D) materials have
been well developed for polarization-sensitive
photodetection, while new 2D members used in shortwave region (>2.5
eV) still remain scarce. The family of 2D hybrid perovskite ferroelectrics,
in which the coupling of spontaneous polarization (Ps) and light benefits dissociation of photoinduced carriers,
has shown great potential in this portfolio. Here, we report a new
2D hybrid perovskite ferroelectric, [CH3(CH2)3NH3]2(CH3NH3)­Pb2Br7 (1), which exhibits a
superior Ps of 3.6 μC/cm2 and a relatively wide bandgap (∼2.55 eV). The unique 2D perovskite
motif results in an intrinsic anisotropy of optical absorption (the
ratio αc/αa ≈ 1.9 at 405
nm), involving its polarization-sensitive activity. As expected, the
strongest photoresponses were observed along the c-axis (i.e., parallel to Ps), along with
a large dichroism ratio (Iphc/Ipha ≈ 2.0) and highly sensitive
detectivity up to ∼109 Jones. Further, crystal-device
of 1 shows a fast responding rate (∼20 μs) and excellent
antifatigued merits. As pioneering work, 1 is the first
polarization-sensitive ferroelectric in the new branch of 2D hybrid
perovskites. Such intriguing behaviors make 1 a potential
candidate for the shortwave polarized-light detection, which also
sheds light on new functionalities for future optoelectronic application
of hybrid perovskites.